When the user of a client terminal connected to the Internet wants to access the information or services offered by service providers on the Internet, the client terminal initiating the connection to the service provider's server needs to identify that server by its Internet Protocol (IP) address (e.g., 123.456.78.9), or by its Internet name (e.g., host.ab.att.com), or as more recently known to the public at large, by its URL that includes an address (e.g., www.host.ab.att.com). A special server, called a domain name server (DNS) is used, as part of the Internet protocol specifications, to map such Internet names to actual IP addresses. There is a non-ambiguous one-to-one mapping function between each name and its associated IP address. In order for such mapping functionality to take place, the IP address of at least one DNS must be known to the application program, such as a Web browser running on the client terminal, which may use the same DNS IP address for each name-to-address mapping lookup. Once the client terminal obtains the IP address of the server with which it wants to interact, a connection is established between the client application and that server application at that IP address. Thus, when a client terminal wants to obtain information or a service from a Web server with a known Internet name on the Internet, the Web browser running on the client terminal transmits that Internet name to the DNS, obtains the IP address associated with that Internet name, and establishes a connection with the Web server at that IP address in order to receive that server's web page.
A connection can also be established on the Internet between two client applications on client terminals if the client terminal initiating the connection knows the IP address of the client terminal at the terminating end of the connection. Each client terminal communicating on the Internet has an IP address assigned to it. This IP address may be a static address that is assigned to the communicating party and remains with that party for a long period of time. Alternatively, a temporary IP address may be dynamically assigned to a client terminal for use for only a short period of time. Generally, when the user of a client terminal accesses the Internet through an Internet Access Service Provider (IASP), the client terminal is assigned an IP address for use only during the user's current session. At the end of that session, the IP address assigned to that client terminal is assigned by the IASP to another client terminal when it establishes a connection with the IASP. Thus, the IASP need not have as many IP addresses as it has customers since only a fraction of its customers are simultaneously connected to it.